scholarly journals Numerical Modeling of Transcritical and Supercritical Fuel Injections Using a Multi-Component Two-Phase Flow Model

Energies ◽  
2020 ◽  
Vol 13 (21) ◽  
pp. 5676
Author(s):  
Bittagowdanahalli Manjegowda Ningegowda ◽  
Faniry Nadia Zazaravaka Rahantamialisoa ◽  
Adrian Pandal ◽  
Hrvoje Jasak ◽  
Hong Geun Im ◽  
...  
Keyword(s):  
Transport Model ◽  
Numerical Study ◽  
Chamber Pressure ◽  
Reacting Flow ◽  
Mixing Processes ◽  
Two Phase ◽  
Flow Solver ◽  
Cubic Equation ◽  
Real Fluid ◽  
Quantitative Analyses

In the present numerical study, implicit large eddy simulations (LES) of non-reacting multi-components mixing processes of cryogenic nitrogen and n-dodecane fuel injections under transcritical and supercritical conditions are carried out, using a modified reacting flow solver, originally available in the open source software OpenFOAM®. To this end, the Peng-Robinson (PR) cubic equation of state (EOS) is considered and the solver is modified to account for the real-fluid thermodynamics. At high pressure conditions, the variable transport properties such as dynamic viscosity and thermal conductivity are accurately computed using the Chung transport model. To deal with the multicomponent species mixing, molar averaged homogeneous classical mixing rules are used. For the velocity-pressure coupling, a PIMPLE based compressible algorithm is employed. For both cryogenic and non-cryogenic fuel injections, qualitative and quantitative analyses are performed, and the results show significant effects of the chamber pressure on the mixing processes and entrainment rates. The capability of the proposed numerical model to handle multicomponent species mixing with real-fluid thermophysical properties is demonstrated, in both supercritical and transcritical regimes.

A Numerical Study of Concurrent Flame Propagation Over Methanol Pool Surface

2012 ◽  
Vol 134 (4) ◽  
Author(s):  
Seik Mansoor Ali ◽  
Vasudevan Raghavan ◽  
K. Velusamy ◽  
Shaligram Tiwari
Keyword(s):  
Flame Spread ◽  
Numerical Study ◽  
Leading Edge ◽  
Reacting Flow ◽  
Atmospheric Conditions ◽  
Air Velocity ◽  
Two Phase ◽  
Spread Velocity ◽  
Pool Surface ◽  
Initial Flame

Concurrent flame spread over methanol pool surface under atmospheric conditions and normal gravity has been numerically investigated using a transient, two-phase, reacting flow model. The average flame spread velocities for different concurrent air velocities predicted using the model are quite close to the experimental data available in the literature. As the air velocity is increased, the fuel consumption rate increases and aids in faster flame spread process. The flame initially anchors around the leading edge of the pool and the flame tip spreads over the pool surface. The rate of propagation of flame tip along the surface is seen to be steady without fluctuations. The flame spread velocity is found to be nonuniform as the flame spreads along the pool surface. The flame spread velocity is seen to be higher initially. It then decreases up to a point when the flame has propagated to around 40% to 50% of the pool length. At this position, a secondary flame anchoring point is observed, which propagates toward the trailing edge of the pool. As a result, there is an increasing trend observed in the flame spread velocity. As the air velocity is increased, the initial flame anchoring point moves downstream of the leading edge of the fuel pool. The variations of interface quantities depend on the initial flame anchoring location and the attainment of thermodynamic equilibrium between the liquid- and gas-phases.

scholarly journals Numerical Study on the Temporal Discretization Schemes in Two-Phase Wave Simulation

2019 ◽  
Author(s):  
Young Jun Kim ◽  
Benjamin Bouscasse ◽  
Sopheak Seng ◽  
David Le Touze
Keyword(s):  
Viscous Flow ◽  
Numerical Study ◽  
Second Order ◽  
Linear Wave ◽  
Two Dimensional ◽  
Discretization Scheme ◽  
Two Phase ◽  
Flow Solver ◽  
Temporal Discretization ◽  
Discretization Schemes

Abstract The generation and propagation of waves in a viscous flow solver are indispensable part of naval computational fluid dynamic (CFD) applications. This paper presents numerical simulations of two-dimensional wave propagation in the framework of two-phase finite volume method (FVM) with different temporal discretization schemes. Implicit Euler, Crank-Nicolson (CN) and second-order backward temporal discretization schemes are compared by using viscous flow solver based on the open source library OpenFOAM. The combinations of each temporal discretization scheme and explicit limiter are used for the formulation of the Volume Of Fluid (VOF) field convection equation. A new formulation using the second-order backward temporal discretization scheme with explicit limiter are investigated. Two-dimensional periodic domains are considered to compare different time-stepping methods. Also, five different refinement levels of meshes are used to study the convergence properties of each method. The non-linear wave is generated with stream function wave theory using ‘foamStar’, which is a specialized OpenFOAM library package developed by Bureau Veritas in collaboration with École Centrale de Nantes.

Numerical Study of a 3D Two-Phase PEM Fuel Cell Model Via a Novel Automated Finite Element/Finite Volume Program Generator

2012 ◽  
Vol 11 (1) ◽  
pp. 65-98 ◽  
Author(s):  
Pengtao Sun ◽  
Su Zhou ◽  
Qiya Hu ◽  
Guoping Liang
Keyword(s):  
Finite Element ◽  
Fuel Cell ◽  
Finite Volume ◽  
Transport Model ◽  
Numerical Study ◽  
Proton Exchange ◽  
Two Phase ◽  
Kirchhoff Transformation ◽  
Phase Transport ◽  
Program Generator

AbstractNumerical methods of a 3D multiphysics, two-phase transport model of proton exchange membrane fuel cell (PEMFC) is studied in this paper. Due to the coexistence of multiphase regions, the standard finite element/finite volume method may fail to obtain a convergent nonlinear iteration for a two-phase transport model of PEMFC [49,50]. By introducing Kirchhoff transformation technique and a combined finite element-upwind finite volume approach, we efficiently achieve a fast convergence and reasonable solutions for this multiphase, multiphysics PEMFC model. Numerical implementation is done by using a novel automated finite element/finite volume program generator (FEPG). By virtue of a high-level algorithm description language (script), component programming and human intelligence technologies, FEPG can quickly generate finite element/finite volume source code for PEMFC simulation. Thus, one can focus on the efficient algorithm research without being distracted by the tedious computer programming on finite element/finite volume methods. Numerical success confirms that FEPG is an efficient tool for both algorithm research and software development of a 3D, multiphysics PEMFC model with multicomponent and multiphase mechanism.

Numerical Study of HVAB Rotor Using a Mixed Mesh Flow Solver

2021 ◽  
Author(s):  
Sang Hyun Park ◽  
Jaeseong Han ◽  
Oh Joon Kwon
Keyword(s):  
Numerical Study ◽  
Flow Solver

Transport of organochlorine pesticides in soil columns enhanced by dissolved organic carbon

1997 ◽  
Vol 35 (7) ◽  
pp. 139-145 ◽  
Author(s):  
Jiann-Yuan Ding ◽  
Shian-Chee Wu
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Organochlorine Pesticides ◽  
Transport Model ◽  
Phase Model ◽  
Soil Columns ◽  
Two Phase ◽  
Three Phase ◽  
Phase Transport ◽  
Remediation Of Soil

The objective of this study is to quantify the effects of humic acid solution infiltration on the transport of organochlorine pesticides (OCPs) in soil columns using a three-phase transport model. From experimental results, it is found that the dissolved organic carbon enhances the transport of OCPs in the soil columns. In the OCPs-only column, the concentration profiles of OCPs can be simulated well using a two-phase transport model with numerical method or analytical solution. In the OCPs-DOC column, the migrations of aldrin, DDT and its daughter compounds are faster than those in the OCPs-only column. The simulation with the three-phase model is more accurate than that with the two-phase model. In addition, significant decrease of the fluid pore velocities of the OCPs-DOC column was found. When DOC leachate is applied for remediation of soil or groundwater pollution, the decrease of mean pore velocities will be a crucial affecting factor.

scholarly journals Numerical Study of a Cooling System Using Phase Change of a Refrigerant in a Thermosyphon

Energies ◽  
2021 ◽  
Vol 14 (12) ◽  
pp. 3634
Author(s):  
Grzegorz Czerwiński ◽  
Jerzy Wołoszyn
Keyword(s):  
Mass Transfer ◽  
Phase Change ◽  
Heat Dissipation ◽  
Cooling System ◽  
Numerical Study ◽  
Relaxation Parameter ◽  
Phase Changes ◽  
Transfer Time ◽  
Two Phase ◽  
Time Relaxation

With the increasing trend toward the miniaturization of electronic devices, the issue of heat dissipation becomes essential. The use of phase changes in a two-phase closed thermosyphon (TPCT) enables a significant reduction in the heat generated even at high temperatures. In this paper, we propose a modification of the evaporation–condensation model implemented in ANSYS Fluent. The modification was to manipulate the value of the mass transfer time relaxation parameter for evaporation and condensation. The developed model in the form of a UDF script allowed the introduction of additional source equations, and the obtained solution is compared with the results available in the literature. The variable value of the mass transfer time relaxation parameter during condensation rc depending on the density of the liquid and vapour phase was taken into account in the calculations. However, compared to previous numerical studies, more accurate modelling of the phase change phenomenon of the medium in the thermosyphon was possible by adopting a mass transfer time relaxation parameter during evaporation re = 1. The assumption of ten-fold higher values resulted in overestimated temperature values in all sections of the thermosyphon. Hence, the coefficient re should be selected individually depending on the case under study. A too large value may cause difficulties in obtaining the convergence of solutions, which, in the case of numerical grids with many elements (especially three-dimensional), significantly increases the computation time.

scholarly journals Numerical Study on an Interface Compression Method for the Volume of Fluid Approach

Fluids ◽  
2021 ◽  
Vol 6 (2) ◽  
pp. 80
Author(s):  
Yuria Okagaki ◽  
Taisuke Yonomoto ◽  
Masahiro Ishigaki ◽  
Yoshiyasu Hirose
Keyword(s):  
Linear Theory ◽  
Volume Fraction ◽  
Numerical Study ◽  
Volume Of Fluid ◽  
Interfacial Wave ◽  
Validation Process ◽  
Two Phase ◽  
Numerical Diffusion ◽  
Mesh Resolution ◽  
Water Reactors

Many thermohydraulic issues about the safety of light water reactors are related to complicated two-phase flow phenomena. In these phenomena, computational fluid dynamics (CFD) analysis using the volume of fluid (VOF) method causes numerical diffusion generated by the first-order upwind scheme used in the convection term of the volume fraction equation. Thus, in this study, we focused on an interface compression (IC) method for such a VOF approach; this technique prevents numerical diffusion issues and maintains boundedness and conservation with negative diffusion. First, on a sufficiently high mesh resolution and without the IC method, the validation process was considered by comparing the amplitude growth of the interfacial wave between a two-dimensional gas sheet and a quiescent liquid using the linear theory. The disturbance growth rates were consistent with the linear theory, and the validation process was considered appropriate. Then, this validation process confirmed the effects of the IC method on numerical diffusion, and we derived the optimum value of the IC coefficient, which is the parameter that controls the numerical diffusion.

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